Web-footed Grating Reduces Loss

IBARAKI, Japan -- A novel arrayed-waveguide grating developed at NTT Photonics Laboratories promises lower insertion losses and crosstalk for filters, multiplexers and demultiplexers in dense wavelength division multiplexing applications. The grating, which the designers presented in the Sept. 9 issue of IEEE Photonics Technology Letters, incorporates vertically tapered waveguides at the junction of the arrayed waveguides and the slab.

The researchers say that no new techniques are required to manufacture the structures, which they describe as web-footed. They fabricated a 32-channel grating with 100-GHz spacings out of silica-based glass using flame hydrolysis deposition, photolithography and reactive ion etching. The device displayed an insertion loss of less than 1 dB, background crosstalk of ­40 dB and polarization-independent operation.